Am 12.07.2015 um 21:14 schrieb Rich Freeman: > On Sun, Jul 12, 2015 at 12:32 PM, Volker Armin Hemmann > <volkerar...@googlemail.com> wrote: >> actually 1 time is enough. With zeros. Or ones. Does not matter at all. >> > That depends on your threat model.
nope. It doesn't. You believe in some urban legend you never dared to question. > > If you're concerned about somebody reading the contents of the drive > using the standard ATA commands, then once with zeros is just fine. > Secure erase is probably easier/faster. > > If you're concerned about somebody removing the disks from the drive > and reading them with specialized equipment then you really want > multiple rounds of complete overwrites with random data. Even then > you run the risk of relocation blocks and all that stuff, so the > secure erase at the end is still a wise move but it may or may not > completely do the job. even then one time is enough. Links are below. > > If you're concerned about somebody leaving the disks in the drive but > having access to directly manipulate the drive heads to possibly > access data not accessible using the standard ATA commands then one > pass is probably good enough, but I'd still use random data instead of > zeros. The reason is that a clever firmware (especially on an SSD) > might not actually record zeros to the regular disk space, but instead > just mark the block range as containing zeros, leaving the actual data > intact. For random data the drive has to actually store the contents > as it cannot be represented in any more concise way. > > If I'm not in a rush I prefer to just do the multiple passes. Why > take a chance? if you do it, it is your problem, but recommending something stupid is something else altogether. > > And of course full-disk encryption is the solution to all of the > above, as it defeats any kind of attack at the level of the drive and > is proactive in nature. > cute. Unlike you, I read some stuff before posting. This is OLD NEWS: http://www.howtogeek.com/115573/htg-explains-why-you-only-have-to-wipe-a-disk-once-to-erase-it/ http://www.vidarholen.net/~vidar/overwriting_hard_drive_data.pdf to quote: " Resultantly, if there is less than a 1% chance of determining each character to be recovered correctly, the chance of a complete 5-character word being recovered drops exponentially to 8.463E-11 (or less on a used drive and who uses a new raw drive format). This results in a probability of less than 1 chance in 10Exp50 of recovering any useful data. So close to zero for all intents and definitely not within the realm of use for forensic presentation to a court. " 10^50. Think about that for a moment. And that is not 'all the data' but 'any useful data'.
